FIX: It takes a long time to compile a query and add it to the Query Store in SQL Server 2016

Symptoms

When you compile a query and add it to the Query Store in SQL Server 2016, there can be significant wait times on mutex for accessing the hash map where statements are stored. Therefore, it may take a long time to finish this operation.

Cause

This problem is caused by a lock contention issue in the Query Store, where new queries are blocked when they are added to the Query Store. This fix replaces the SEList element with SEListSized, which explicitly holds the number of elements in the list.

Resolution

The issue was first fixed in the following cumulative update of SQL Server: